1. Field of the Invention
The present invention relates to a ceramic hybrid lens formed by affixing a plastic lens formed of a layer of resin to a surface of a ceramic lens which is an polishing lens.
2. Description of the Related Art
In recent years, as small and high-performance optical lenses, many aspherical lenses have been used for cameras and reading and recording optical equipment for compact discs.
As the aspherical lenses, many hybrid lenses are used in which a plastic lens of an ultraviolet curing resin is affixed to a surface of a ground or cut glass lens.
To be specific, the hybrid lenses are formed by coating a required amount of ultraviolet curing resin to a mold on which an aspherical surface is formed, placing a glass lens on the resin to extend the resin that has not yet cured so that a lower portion of the resin follows the shape of the mold and is tightly joined to the glass lens, radiating a violet ray from the glass lens side to cure the resin, and removing the resin from the mold after the resin has cured to complete the molding of a plastic lens which is tightly joined to the glass lens, whereby a hybrid lens is obtained in which the plastic lens is affixed to the glass lens.
In the hybrid lens so made, in order to prevent the separation of the plastic lens from the glass lens, it is proposed to mold an aspherical lens by finishing slightly roughly a surface of the glass lens which is to be bonded to the plastic lens when the glass lens is ground or cut and using glass and ultraviolet curing resin materials which can provide refractive indices which are close to each other (for example, Patent Document No. 1).
[Patent Document No. 1] Japanese Unexamined Patent Publication No. 2000-180602
As has been described above, by forming a lens into an aspherical one, a small and high-performance optical lens can be manufactured, and the hybrid lens, in which the plastic lens whose surface is shaped through molding using a mold is formed on the surface thereof, has several advantages: the hybrid lens so made is superior in shaping performance to shape the lens into the aspherical shape to match its application, in mass production and in environment performance in that the hybrid lens is not much affected by environmental factors such as humidity. However, some consideration needs to be made to prevent the separation of the plastic lens from the glass lens on the surface of which the plastic lens is formed.
Due to this, while the surface of the glass lens is made slightly rough to thereby spend no time in grinding, as well as increasing the joining force with which the glass lens is joined to the plastic lens, in this event, since the lens performance is reduced in case materials are not used in which the refractive index of a glass which constitutes a glass material for the glass lens and the refractive index of an ultraviolet curing resin which constitutes a material for the plastic lens are close to each other, there exists an inherent drawback that the refractive index of the lens is limited.
In addition, in the event that the refractive indices of glass and resin are different, when the lens performance is increased by finishing the surface of the glass smooth by polishing, the glass lens and the plastic lens tend to be easily separated from each other, and to cope with this, manhours are increased for surface treatment of the glass lens and adjustment of radiating conditions of ultraviolet rays, leading to a problem that the productivity is deteriorated.
The invention was made to solve the problems and an object thereof is to provide a hybrid lens having a high refractive index and a high performance.